According to the historian José Luis Rodríguez Jiménez, [T]he concept of "bunker" refers to a group of influential people in entrenched positions and established in the institutions of the Francoist State.
The term was used for the first time in 1968 in an article published in the newspaper ABC by its director, Torcuato Luca de Tena, to refer to those who opposed the evolution of the Franco regime and opening up to Europe.
The búnker began form in 1974, the year before the death of Francisco Franco, although some authors trace its genesis to 1970, coinciding with the first signs of exhaustion of the regime and the voices that clamored for its reform.
This opposition was expressed through opinion articles in related media, the most prominent being the one signed by Girón de Velasco in the newspaper Arriba on April 28, 1974, popularly known as the Gironazo, thus putting an end to any attempt at reform and precipitating the dismissal of the pro-reform Minister of Information and Tourism Pío Cabanillas.
Before Franco's death, there was still pressure for the Crown to fall not on the designated heir Juan Carlos, but on his cousin, Alfonso, Duke of Anjou and Cádiz, at the time married to the dictator's granddaughter, María del Carmen Martínez-Bordiú.